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<H4>POSIX Threads for Windows – REFERENCE - <A HREF="https://sourceforge.net/projects/pthreads4w/">Pthreads4W</A></H4>
<P><A HREF="index.html">Reference Index</A></P>
<P><A HREF="#toc">Table of Contents</A></P>
<H2><A HREF="#toc0" NAME="sect0">Name</A></H2>
<P>pthread_rwlock_unlock - unlock a read-write lock object 
</P>
<H2><A HREF="#toc1" NAME="sect1">Synopsis</A></H2>
<P><B>#include &lt;pthread.h&gt; </B>
</P>
<P>in<B>t pthread_rwlock_unlock(pthread_rwlock_t <I>*</I></B><I>rwlock</I><B>);
</B>
</P>
<H2><A HREF="#toc2" NAME="sect2">Description</A></H2>
<P>The <B>pthread_rwlock_unlock</B> function shall release a lock
held on the read-write lock object referenced by <I>rwlock</I>.
Results are undefined if the read-write lock <I>rwlock</I> is not
held by the calling thread. 
</P>
<P>If this function is called to release a read lock from the
read-write lock object and there are other read locks currently held
on this read-write lock object, the read-write lock object remains in
the read locked state. If this function releases the last read lock
for this read-write lock object, the read-write lock object shall be
put in the unlocked state with no owners. 
</P>
<P>If this function is called to release a write lock for this
read-write lock object, the read-write lock object shall be put in
the unlocked state. 
</P>
<P><B>PThreads4W</B> does not prefer either writers or readers in
acquiring the lock – all threads enter a single prioritised FIFO
queue. While this may not be optimally efficient for some
applications, it does ensure that one type does not starve the other.</P>
<P>Results are undefined if any of these functions are called with an
uninitialized read-write lock. 
</P>
<P><B>PThreads4W</B> defines <B>_POSIX_READER_WRITER_LOCKS</B> in
pthread.h as  200112L to indicate that the reader/writer routines are
implemented and may be used.</P>
<H2><A HREF="#toc3" NAME="sect3">Return Value</A></H2>
<P>If successful, the <B>pthread_rwlock_unlock</B> function shall
return zero; otherwise, an error number shall be returned to indicate
the error. 
</P>
<H2><A HREF="#toc4" NAME="sect4">Errors</A></H2>
<P>The <B>pthread_rwlock_unlock</B> function may fail if: 
</P>
<DL>
	<DT><B>EINVAL</B> 
	</DT><DD>
	The value specified by <I>rwlock</I> does not refer to an
	initialized read-write lock object. 
	</DD><DD STYLE="margin-left: 0cm; margin-bottom: 0.5cm">
	<BR><BR>
	</DD></DL>
<P>
The <B>pthread_rwlock_unlock</B> function shall not return an error
code of [EINTR]. 
</P>
<P><I>The following sections are informative.</I> 
</P>
<H2><A HREF="#toc5" NAME="sect5">Examples</A></H2>
<P>None. 
</P>
<H2><A HREF="#toc6" NAME="sect6">Application Usage</A></H2>
<P>None. 
</P>
<H2><A HREF="#toc7" NAME="sect7">Rationale</A></H2>
<P>None. 
</P>
<H2><A HREF="#toc8" NAME="sect8">Future Directions</A></H2>
<P>None. 
</P>
<H2><A HREF="#toc9" NAME="sect9">See Also</A></H2>
<P><A HREF="pthread_rwlock_init.html"><B>pthread_rwlock_destroy</B>(3)</A>
<B>,</B> <A HREF="pthread_rwlock_rdlock.html"><B>pthread_rwlock_rdlock</B>(3)</A>
<B>,</B> <A HREF="pthread_rwlock_timedrdlock.html"><B>pthread_rwlock_timedrdlock</B>(3)</A>
<B>,</B> <A HREF="pthread_rwlock_timedwrlock.html"><B>pthread_rwlock_timedwrlock</B>(3)</A>
<B>,</B> <A HREF="pthread_rwlock_rdlock.html"><B>pthread_rwlock_tryrdlock</B>(3)</A>
<B>,</B> <A HREF="pthread_rwlock_wrlock.html"><B>pthread_rwlock_trywrlock</B>(3)</A>
<B>,</B> <A HREF="pthread_rwlock_wrlock.html"><B>pthread_rwlock_wrlock</B>(3)</A>
, the Base Definitions volume of IEEE&nbsp;Std&nbsp;1003.1-2001,
<I>&lt;pthread.h&gt;</I> 
</P>
<H2><A HREF="#toc10" NAME="sect10">Copyright</A></H2>
<P>Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1, 2003 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. In the event of any discrepancy between this version and the
original IEEE and The Open Group Standard, the original IEEE and The
Open Group Standard is the referee document. The original Standard
can be obtained online at <A HREF="http://www.opengroup.org/unix/online.html">http://www.opengroup.org/unix/online.html</A>
. 
</P>
<P>Modified by Ross Johnson for use with <A HREF="https://sourceforge.net/projects/pthreads4w/">Pthreads4W</A>.</P>
<HR>
<P><A NAME="toc"></A><B>Table of Contents</B></P>
<UL>
	<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect0" NAME="toc0">Name</A>
		</P>
	<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect1" NAME="toc1">Synopsis</A>
		</P>
	<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect2" NAME="toc2">Description</A>
		</P>
	<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect3" NAME="toc3">Return
	Value</A> 
	</P>
	<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect4" NAME="toc4">Errors</A>
		</P>
	<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect5" NAME="toc5">Examples</A>
		</P>
	<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect6" NAME="toc6">Application
	Usage</A> 
	</P>
	<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect7" NAME="toc7">Rationale</A>
		</P>
	<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect8" NAME="toc8">Future
	Directions</A> 
	</P>
	<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect9" NAME="toc9">See
	Also</A> 
	</P>
	<LI><P><A HREF="#sect10" NAME="toc10">Copyright</A> 
	</P>
</UL>
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